Extrapulmonary TB occurs in 10-20% of HIV-seronegative persons with active TB. The pathogenesis of extrapulmonary or disseminated TB in HIV-seronegative persons is not well understood, however. Case reports of infections due to nontuberculous mycobacteria in HIV-seronegative children have helped to elucidate potential mechanisms of disseminated mycobacterial infections. Both interferon (IFN)-gamma and interleukin (IL)-12 appear to play a crucial role in the susceptivility to these infections. Specific immune defects which predispose to extrapulmonary TB have not been identified, however. We seek a better understanding of the cytokine responses in the interferon-gamma pathway, to identify specific defects which may predispose to extrapulmonary or disseminated TB.